Mechanical press device

ABSTRACT

The invention provides a mechanical press apparatus for both single and double uses which can press mold a large-sized blank at a high pressure by employing a single action use aspect while being of a double action type. In a mechanical press apparatus provided with a drive portion ( 14 ) which moves upward and downward an outer slide ( 8 ) and an inner slide ( 9 ) arranged in an inner side of the outer slide at a predetermined timing, an elevating plate ( 10 ) is fixed to a lower end surface of the outer slide ( 8 ) so as to oppose to a lower surface of the inner slide ( 9 ), and the lower surface is provided with an upper die ( 7 ) and a lower die ( 3 ) positioned at a lower surface thereof so as to press. Further, an upper surface portion of the elevating plate ( 10 ) is provided with a first hydraulic cylinder ( 11 ) contracted by a pressing force at a time when the inner slide ( 9 ) moves downward. Further, a second hydraulic cylinder ( 12 ) is provided between the outer slide ( 8 ) and the drive portion ( 14 ) so as to be expanded working with a pressure of a pressurized fluid supplied from the first hydraulic cylinder ( 11 ) at a time when the first hydraulic cylinder ( 11 ) is contracted by the pressing force of the inner slide ( 9 ), thereby pressing the outer slide ( 8 ) to a lower side.

TECHNICAL FIELD

The present invention relates to a mechanical press apparatus, and moreparticularly to a mechanical press apparatus which can be used in asingle action aspect while being of a double action type.

BACKGROUND OF THE INVENTION

A press apparatus served for a drawing process of a steel plate isconventionally classified broadly into a hydraulic press apparatus usinga hydraulic pressure, and a mechanical press apparatus on the basis of amechanical drive force by a pressure generating mechanism, however, theyare classified into a single action type and a double action type on thebasis of a motion type of a slide. Further, the mechanical pressapparatus is classified into a crank press, a knuckle press, a linkpress, a friction press and the like on the basis of a drive mechanismof the slide.

Among the structures mentioned above, the double action type mechanicalpress apparatus is structured such that an outer slide and an innerslide provided in an inner side of the outer slide are independentlymoved upward and downward by a drive portion, the outer slide movesdownward prior to the inner slide at a time of pressing a blank, anouter die attached thereto presses a peripheral edge portion of theblank, and a draw molding or the like of the blank is next performed bythe downward movement of the inner slide (refer, for example, toJapanese Unexamined Patent Publication No. 8-103827).

As mentioned above, in the conventional mechanical press apparatus onthe basis of the double action type, since the outer slide presses theblank prior to the inner slide, there is an advantage that a deepdrawing of the blank can be stably and well achieved in comparison withthe single action type.

However, the conventional mechanical press apparatus on the basis of thedouble action type requires two molds for each of upper and lower molds,such as an outer die and an inner die (a punch) serving as the uppermold, and a blank holder corresponding to the outer die and a cavitycorresponding to the inner die serving as the lower mold, and astructure of the drive portion is complex in comparison with the singleaction type. Accordingly, there is a disadvantage that a high cost isrequired.

Further, the conventional mechanical press apparatus on the basis of thedouble action type is generally placed at the head of a tandem line inorder to suit for a deep drawing, and the single action type generallyforms the blank in a convex shape. On the contrary, since the doubleaction type performs a concave shape, it is necessary to reverse upperand lower surfaces of the blank by equipping a turn-over device betweenthe double action type and the single action type. Accordingly, there isa problem that a productivity of the press molded product isdeteriorated.

In particular, in the conventional mechanical press apparatus on thebasis of the double action type, since a drive force distributed to theouter slide and the inner slide is determined by the structure of thedrive portion, a pressing capacity of the outer slide and the innerslide can not be changed in correspondence to a material and a thicknessof the blank. Further, if the inner die is enlarged, the inner die isinterfered with the outer die. Accordingly, a product pressed thereby islimited to a magnitude of an inner side of the outer slide.

Accordingly, in recent years, the single action type press apparatus ismainly employed for the purpose of corresponding to an increase in sizeof the press molded product such as a motor vehicle body or the like andimproving a productivity, and the mechanical press apparatus which is ofthe double action type, has a small pressing capacity and is hard to bemodified for increasing the capacity is not used very much, and is underan actual condition of being anxious about a countermeasure thereof.

The present invention is made by taking the circumstances mentionedabove into consideration, and an object of the present invention is tomake it possible to preferably press mold a large-sized blank at a highpressure by employing a single action use aspect while being of a doubleaction type.

SUMMARY OF THE INVENTION

In order to achieve the object mentioned above, in accordance with thepresent invention, there is provided a mechanical press apparatusprovided with a drive portion which moves upward and downward an outerslide and an inner slide arranged in an inner side of the outer slide ata predetermined timing, comprising:

an elevating plate fixed to a lower end surface of the outer slide so asto oppose to a lower surface of the inner slide;

an upper die (an upper mold) fixed to a lower surface of the elevatingplate;

a lower die (a lower mold) positioned at a lower surface of an upwardand downward movement of the upper die so as to press;

a first hydraulic cylinder provided in an upper surface portion of theelevating plate and contracted by a pressing force at a time when theinner slide moves downward; and

a second hydraulic cylinder interposed between the outer slide and thedrive portion and expanded working with a pressure of a pressurizedfluid supplied from the first hydraulic cylinder at a time when thefirst hydraulic cylinder is contracted by the pressing force of theinner slide, thereby pressing the outer slide to a lower side.

In this case, it is preferable that each of the first hydraulic cylinderand the second hydraulic cylinder is of a single rod type having anexpansion rod integrally provided with a piston portion which isreciprocated in a longitudinal direction in an inner portion of a hollowand sealed cylinder barrel so as to expand and compress a fluid in aninner portion, and a rod portion which is extended from the pistonportion to an outer portion of the cylinder barrel, and of a doubleaction type having a primary port supplying and discharging the expandedand compressed fluid to a side of the piston portion of the expansionrod and a secondary port supplying and discharging the fluid in a sideof the rod portion of the expansion rod in the cylinder barrel, and thecylinder barrels of the first hydraulic cylinder and the secondhydraulic cylinder are connected in the primary ports to each other viaa consecutive passage, and work with each other such that thepressurized fluid flows into the second hydraulic cylinder via theconsecutive passage at a time when the first hydraulic cylinder iscontracted, thereby expanding the expansion rod.

Further, it is preferable that a rate A1/A2 between a pressure receivingarea A1 of the first hydraulic cylinder (the piston portion) and apressure receiving area A2 of the second hydraulic cylinder (the pistonportion) is set to be equal to a rate P1/P2 between a pressing capacityP1 of the inner slide and a pressing capacity P2 of the outer slide.

Further, it is preferable that a first pipe line for supplying thepressurized fluid having a predetermined pressure from a pressure sourceis connected to an area of the consecutive passage connecting theprimary ports of the first hydraulic cylinder and the second hydrauliccylinder to each other, a second pipe line for supplying the pressurizedfluid having a higher pressure than that of the pressurized fluidsupplied to the first pipe line from the pressure source so as to returnto the state before being communicated is connected to the secondaryport of the second hydraulic cylinder, and the secondary port of thefirst hydraulic cylinder is provided so as to supply and discharge anair serving as the fluid in correspondence to the motion thereof.

Further, it is preferable that the first hydraulic cylinder is providedso as to be actuated only by the primary port with canceling thesecondary port.

Further, it is preferable that a die set portion for coupling the upperdie is provided in the lower surface of the elevating plate.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1]

FIG. 1 is a schematic view showing an embodiment of a mechanical pressapparatus in accordance with the present invention.

[FIG. 2]

FIG. 2 is a side elevational view showing an example of a structure of adrive portion shown in FIG. 1 as seen by a vertical cross section.

[FIG. 3]

FIG. 3 is a front elevational view showing an example of the structureof the drive portion shown in FIG. 1 as seen by partly cutting along afront surface.

[FIG. 4]

FIG. 4 is a cross sectional view showing a cross section along a lineX—X shown in FIG. 3.

[FIG. 5]

FIG. 5 is a schematic view showing a mounting portion of an upper dieshown in FIG. 1.

[FIG. 6]

FIG. 6 is a circuit diagram showing an embodiment of a hydraulic circuitexecuting a pressure control within first and second hydraulic cylindersshown in FIG. 5.

[FIGS. 7A–7D]

FIGS. 7A–7D are schematic views explaining a working operation of ablank by the mechanical press apparatus shown in FIG. 1.

[FIG. 8]

FIG. 8 is a cycle curve of an outer slide and an inner slide.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Descriptions will be in detail given below of embodiments of mechanicalpress apparatus in accordance with the present invention with referenceto the accompanying drawings. First, FIG. 1 is a schematic view showingthe embodiment of the mechanical press apparatus in accordance with thepresent invention. In FIG. 1, reference numeral 1 denotes a bed,reference numeral 2 denotes a bolster fixed on the bed, referencenumeral 3 denotes a lower die mounted on the bolster 2, and referencenumeral 4 denotes a frame-like blank holder arranged in an outer side ofthe lower die 3. The blank holder 4 is supported by a cushion pin 5passing through the bolster 2, and the cushion pin 5 is supported so asto freely elevate by a die cushion 6 arranged within the bed 1. In thiscase, the blank holder 4, the cushion pin 5 and the die cushion 6 can beomitted as occasion demands.

On the other hand, reference numeral 7 denotes an upper diecorresponding to the lower die 3, and reference numeral 8 denotes aframe-like outer slide elevating the upper die 7. An inner slide 9 isprovided in an inner side of the outer slide 8, and the slides 8 and 9are suspended below a crank shaft 19 mentioned below by a balancecylinder (not shown) so as to freely elevate. In particular, anelevating plate 10 closing a lower opening portion of the outer slide 8is fixed to the outer slide 8, and the structure is made such that theupper die 7 is mounted to a lower surface of the elevating plate 10. Inother words, the upper die 7 (an upper mold) is moved downward to thelower die (a lower mold) positioned at an upward and downward movinglower surface (a top surface of the bolster 2) so as to be fixedthereto, and is formed as a single action type mold structure bypinching a blank W (refer to FIG. 7) therebetween. Therefore, inaccordance with the present embodiment, since it is possible to form byone upper mold and one lower mold comprising the upper die 7 serving asthe upper mold and the lower die 3 serving as the lower mold, a metalmold structure is simple and a cost can be reduced in the same manner asthe single action type. Further, in accordance with the presentembodiment, since the turn-over device is not required even if themechanical press apparatus in accordance with the present invention isplaced at the head of the tandem line on the basis of the single actiontype structure forming the blank W in a convex shape, a productivity ofthe press molded product can be improved. Further, in accordance withthe present embodiment, since it is possible to form by one upper moldand one lower mold as mentioned above, the upper and lower molds are notseparated into the inner die and the outer die as in the double actiontype and are not interfered with each other, whereby it is possible toprevent the press molded product from being limited to the magnitude ofthe inner side of the outer slide. On the other hand, a first hydrauliccylinder 11 is provided in the upper surface portion of the elevatingplate 10, a second hydraulic cylinder 12 is interposed in an upper endsurface of the outer slide 8 with respect to a drive portion 14mentioned below, and the structure is made such that both the hydrauliccylinders 11 and 12 are connected by a consecutive passage 13 so as tobe alternately contracted and expanded in an interlocking manner on thebasis of the supply and the discharge of the pressurized fluid. In thiscase, in the present embodiment, four hydraulic cylinders 11 and 12 areprovided respectively. In other words, the present embodiment is formedas the mechanical press structure for both the single and double actionswhich can achieve the double action type motion while having the singleaction type mold structure, and can press mold even the large-sizedblank W such as the motor vehicle body or the like at a high pressure.

In this case, reference numeral 14 denotes a drive portion moving upwardand downward the outer slide 8 and the inner slide 9 at a predeterminedtiming. The drive portion 14 is constituted by a motor 15 (an electricmotor) forming a drive source, a flywheel 16 storing a drive force, anda transmission mechanism 17 converting a rotational movement of theflywheel 16 into a reciprocating linear movement of the outer slide 8and the inner slide 9. In the present embodiment, the transmissionmechanism 17 is a broad crank mechanism including a link, and isconstituted by a main shaft 18 rotationally driven by the flywheel 16, acrank shaft 19 working with the main shaft, an outer rod 20 forconnecting the crank shaft 19 to the outer slide 8, and an inner rod 21for connecting the crank shaft 19 to the inner slide 9. In this case,reference numeral 22 denotes a clutch provided in one end side of themain shaft 18, and reference numeral 23 denotes a brake apparatusprovided in the other end side of the main shaft 18.

Further, in accordance with the mechanical press apparatus mentionedabove, when the outer slide 8 and the inner slide 9 are moved downwardon the basis of an actuation of the drive portion 14, and the outerslide 8 is moved downward to a predetermined position (a substantialbottom dead center where the upper die 7 is in contact with the blank onthe blank holder 4), the other second hydraulic cylinder 12 is expandedso as to press the outer slide 8 to a lower side on the basis of thecompression of the first hydraulic cylinder 11 caused by the pressingforce of the inner slide 9, at the same time when the inner slide 9presses the elevating plate 10 to a lower side while compressing thefirst hydraulic cylinder 11.

Next, FIG. 2 is a side elevational view showing an example of astructure of the drive portion 14 shown in FIG. 1 as seen by a verticalcross section, and FIG. 3 is a front elevational view showing an exampleof the structure of the drive portion 14 shown in FIG. 1 as seen bypartly notching along a front surface. A description will be given indetail of the example of the structure (the structure which is not shownin FIG. 1) of the drive portion 14 with reference to FIGS. 2 and 3. Apair of pinion gears 24 are fixed to the main shaft 18 so as to leave apredetermined space. Further, a pair of right and left rotary shafts 26are mounted to an apparatus frame 25 so as to be in parallel to the mainshaft 18, and two idle gears 27 of a two-stage structure having alarge-diameter portion 27A and a small-diameter portion 27B are fixed toeach of both the rotary shafts 26. Among them, the large-diameterportions 27A of the adjacent idle gears 27 are engaged with each other,and the pinion gear 24 is engaged with the large-diameter portion 27A ofthe idle gear 27 fixed to one rotary shaft 26. Further, two crank shafts19 are provided in the apparatus frame 25 in a parallel manner along themain shaft 18, and an output gear 28 engaging with the small-diameterportion 27B of the idle gear 27 is mounted to both the crank shaft 19.In this case, the crank shaft 19 is constituted by a crank journal 19Aforming a center of rotation of the output gear 28, an eccentric pin 19Bformed at an eccentric point, a crank arm 19C mounted to the crankjournal 19A, and a crank arm 19D mounted to the eccentric pin 19B.Further, oscillating links 29 and 30 and a connecting rod 31 areconnected to the crank arm 19C in an outer side, and a lower end of theconnecting rod 31 is joined by pin to an upper end of the outer rod 20.Further, an oscillating link 32 is connected to the crank arm 19D in aninner side, and the inner rod 21 is connected to the eccentric pin 19Bvia a connecting rod 33.

In accordance with the drive portion 14 (the transmission mechanism)structured as mentioned above, it is possible to move the rods 20 and 21upward and downward at the predetermined timing on the basis of adifference in the connection aspect of the outer rod 20 and the innerrod 21 with respect to the crank shaft 19.

Next, FIG. 4 is a cross sectional view showing a cross section along aline X—X shown in FIG. 3. As is apparent from the drawing, the outer rod20 is connected to four positions on the upper surface of the outerslide 8, and the inner rod 21 is connected to four positions on theupper surface of the inner slide 9. In this case, in FIG. 4, referencenumeral 34 denotes a column. An outer guide 35 (a slide gib) forming aguide for a reciprocating movement of the outer slide 8 is mounted tothe column 34, and an inner guide 36 (a slide gib) forming a guide ofthe inner slide 9 is mounted to an inner side surface of the outer slide8.

Next, FIG. 5 is a schematic view showing a mounting portion of the upperdie 7 shown in FIG. 1. In this FIG. 5, the elevating plate 10 is formedby a thick steel plate which is equal to or larger than an outerperiphery of the outer slide 8, and is fixed to the lower end surface ofthe outer slide 8 by using bolts or the like. Further, plural grooves ofT-shaped notch grooves 37 are formed as a die set portion mounting theupper die 7 in the lower surface of the elevating plate 10 in a parallelmanner, and the structure is made such that a convex nut 38 mounted tothe upper surface of the upper die 7 is fitted to each of the notchgrooves 37, and a positioning pin 39 is press fitted to the elevatingplate 10 from the upper die 7.

Further, as is apparent from FIG. 5, each of the first hydrauliccylinder 11 and the second hydraulic cylinder 12 is structured as ahydraulic cylinder of a single rod type having an expansion rod 11B or12B integrally provided with a piston portion which is reciprocated in alongitudinal direction in an inner portion of a hollow and sealedcylinder barrel 11A or 12A so as to expand and compress the fluid in theinner portion, and a rod portion which is extended from the pistonportion to an outer portion of the cylinder barrel 11A or 12A, and of adouble action type having a primary port 41 or 42 supplying anddischarging the expanded and compressed fluid to a side of the pistonportion of the expansion rod 11B or 12B and a secondary port 43 or 44supplying and discharging the fluid in a side of the rod portion of theexpansion rod 11B or 12B in the cylinder barrel 11A or 12A. Among them,the cylinder barrel 11A of one first hydraulic cylinder 11 is fixed tothe upper surface portion of the elevating plate 10, and an upper endsurface (a rod portion) of the expansion rod 11B protruding from thecylinder barrel 11A is opposed to the lower surface of the inner slide9, and is controlled so as to keep an expansion and contraction state ata time when the pressing force by the inner slide 9 is not applied.However, the structure may be made such that the expansion rod 11B isfixed to the upper surface portion of the elevating plate 10 by settingthe cylinder barrel 11A upward. Further, in the present embodiment, thefirst hydraulic cylinder 11 is structured such that the expansion rod11B has the piston portion and the rod portion, however, this can bechanged to a plunger type.

On the other hand, the cylinder barrel 12A of the second hydrauliccylinder 12 is mounted to the upper end surface of the outer slide 8 viaa nut 45 and an adjuster bolt 46 so as to be adjustable in height, andan upper end surface (a rod portion) of the expansion rod 12B protrudingfrom the cylinder barrel 12A is fixed to the outer rod 20. Further, theinner rod 21 is connected to the inner slide 9 via a nut 47 and anadjuster bolt 48. In this case, a height adjustment of the respectiveslides 8 and 9 by the adjust bolts 46 and 48 is executed beforeconnecting the outer slide 8 and the inner slide 9 to the outer rod 20and the inner rod 21. In this case, the expansion rod 12B of the secondhydraulic cylinder 12 is also formed as an aspect having the pistonportion and the rod portion, however, the structure may be made suchthat the expansion rod 12B is mounted to the outer slide 8 by settingthe expansion rod 12B downward and the cylinder barrel 12A is fixed tothe outer rod 20.

In this case, in the cylinder barrels 11A and 12A of the first andsecond hydraulic cylinders 11 and 12 as mentioned above, the primaryports 41 and 42 are connected to each other via the consecutive passage13 such that when one first hydraulic cylinder 11 is contracted by thepressing force caused by the downward movement of the main slide 9, theother second hydraulic cylinder 12 is expanded so as to press the outerslide 8 to the lower side. In other words, both ends of the consecutivepassage 13 are respectively connected to the primary ports 41 and 42 ofthe first and second hydraulic cylinders 11 and 12, and when one firsthydraulic cylinder 11 is contracted, the pressurized fluid (a workingfluid) is pushed out from the primary port 41, and flows into the innerportion from the primary port 42 of the other second hydraulic cylinder12 through the consecutive passage 13 so as to generate the pressure forexpanding the expansion rod 12B of the hydraulic cylinder 12 under thecontracted state and achieve an interlock.

In this case, the consecutive passage 13 is constituted by an excavationhole 13A formed within the elevating plate 10 and a pipe 13C connectedvia the block 13B, and the structure is made such that one end of theexcavation hole 13A is connected with the primary port 41 of the firsthydraulic cylinder 11, and another end of the excavation hole 13A andthe primary port 42 of the second hydraulic cylinder 12 are connected bythe pipe 13C. Further, a rate A1/A2 between a pressure receiving area A1of the first hydraulic cylinder 11 (the piston portion) and a pressurereceiving area A2 of the second hydraulic cylinder 12 (the pistonportion) is set to be equal to a rate P1/P2 between a pressing capacityP1 of the inner slide 9 (a force applied to the inner slide 9 from theinner rod 21) and a pressing capacity P2 of the outer slide 8 (a forceapplied to the outer slide 8 from the outer rod 20).

For example, in the case that the pressing capacity P1 of the innerslide 9 is 1600 tons (4×400), and the pressing capacity P2 of the outerslide 8 is 800 tons (4×200), the rate A1/A2 between the pressurereceiving area A1 of the first hydraulic cylinder 11 and the pressurereceiving area A2 of the second hydraulic cylinder 12 is set to 2/1. Inaccordance with this structure, it is possible to apply the pressingforce as large as possible to the outer slide 8 from the above so as toprevent the strain of the elevating plate 10 at a time of pressing theblank, while preventing an overload from being applied to the driveportion 14 (the outer rod 20) from the second hydraulic cylinder 12,whereby it is possible to well executed the press molding by the upperdie 7 mounted to the lower surface.

In this case, an internal pressure of the first and second hydrauliccylinders 11 and 12 can be controlled by a pressure control means (ahydraulic apparatus) including the first and second hydraulic cylinders11 and 12.

FIG. 6 is a circuit diagram showing an embodiment of a hydraulic circuitfor executing a pressure control within the first and second hydrauliccylinders 11 and 12 shown in FIG. 5. In FIG. 6, reference numeral 50denotes a hydraulic unit. The hydraulic unit 50 in accordance with thepresent embodiment is provided with a fixed displacement type hydraulicpump 51 serving as the pressure source, and a motor 52 for driving thehydraulic pump 51. Further, the hydraulic pump 51 is connected to anarea of the consecutive passage 13 (a block 13B constituting theconsecutive passage 13 in the present embodiment) connecting the primaryports 41 and 42 of the first and second hydraulic cylinders 11 and 12via a pipe line 53 (a first pipe line), and the structure is made suchthat the pressurized fluid (the working fluid) having a predeterminedpressure is supplied into the first and second hydraulic cylinders 11and 12 from the hydraulic pump 51. Further, the secondary port 44 of thesecond hydraulic cylinder 12 and the hydraulic pump 51 are connected bya pipe line 54 (a second pipe line), and the structure is made such thatthe pressurized fluid having a higher pressure than that of thepressurized fluid supplied to the pipe line 53 (the first pipe line) issupplied to the inner portion of the second hydraulic cylinder 12 fromthe secondary port 44 through the pipe line 54 from the hydraulic pump51 so as to return to the state before the interlock. Further, thesecondary port 43 (refer to FIG. 5) of the first hydraulic cylinder 11is provided so as to supply and discharge the air serving as the fluidto the side of the rod portion within the cylinder barrel 11A incorrespondence to the interlocking motion mentioned above.

In this case, the first hydraulic cylinder 11 is described in detailwith respect to the embodiment provided with the primary port 41 and thesecondary port 43, however, is not limited to this. For example, thefirst hydraulic cylinder 11 may be provided so as to be actuated only bythe primary port 41 by canceling the secondary port 43.

In this case, an operated directional valve 55, a pressure reducingvalve 56, check valves 57 and 58 and a pressure control valve 59 (arelief valve) are interposed in the first pipe line 53 in sequence froman upstream side, and an operated directional valve 60, check valves 61and 62, an accumulator 63 and a pressure control valve 64 (a reliefvalve) are interposed in the second pipe line 54 in sequence from anupstream side. Among them, the check valves 58 and 62, the accumulator63, and the pressure control valves 59 and 64 structure a control unit65 in correspondence to a set of hydraulic cylinders 11 and 12, however,a working pressure of the pressure control valve 59 in the first pipeline 53 in the control unit 65 is set higher than the pressure controlvalve 64 in the second pipe line 54. In this case, the accumulator 63 isuseful for quickly returning the second hydraulic cylinder 12 at a timewhen the second hydraulic cylinder 12 is expanded, and is essential forquickening SPM (a stroke number per one minute). Further, theaccumulator 63 is useful for absorbing a shock of the oil in the side ofthe secondary port 44, in the case that the oil is transferred from thefirst hydraulic cylinder 11 to the second hydraulic cylinder 12 rapidly.

Further, in accordance with the hydraulic circuit on the basis of thepresent embodiment, when the pressure of the pressurized fluid appliedto the second hydraulic cylinder 12 comes over the set value due to thecontraction of the first hydraulic cylinder 11 caused by the pressingforce of the inner slide 9, it is possible to discharge the pressurizedfluid from the area (the consecutive passage 13) of the first and secondhydraulic cylinders 11 and 12 on the basis of the actuation of thepressure control valve 59 so as to prevent the second hydraulic cylinder12 and the drive portion 14 from being broken. Further, it is possibleto increase a buffering capacity at a time when the second hydrauliccylinder 12 is expanded by the pressurized fluid supplied to theaccumulator 63 from the secondary port 44 of the secondary hydrauliccylinder 12, it is possible to transmit the pressing force of the innerslide 9 to the outer slide 8 with no loss, and it is possible to returnthe first and second hydraulic cylinders 11 and 12 respectively to theexpansion and contraction states at a time when the outer slide 8 andthe inner slide 9 are returned to the top dead center.

A description will be in detail given below of an operation using theembodiment of the mechanical press apparatus in accordance with thepresent invention structured as mentioned above, with reference to FIG.7. FIG. 7 is a schematic view explaining a working operation of theblank W by the mechanical press apparatus shown in FIG. 1, in which FIG.7(A) shows a state before being press molded, FIG. 7(B) shows a state inwhich the upper die 7 is moved downward so as to be brought into contactwith the blank W, FIG. 7(C) shows a state of being press molded, andFIG. 7(D) shows a state after being press molded, respectively. First,in FIG. 7(A), the blank W is mounted on the blank holder 4, and theouter slide 8 and the inner slide 9 are at the top dead center and in astandby state. Further, the outer slide 8 and the inner slide 9 aremoved downward as shown in FIG. 7(B) on the basis of the actuation ofthe drive portion 14 (refer to FIG. 1) from this state. In particular,the outer slide 8 is moved downward at a high speed prior to the innerslide 9, and when the peripheral edge portion of the upper die 7 isbrought into contact with the blank W, the inner slide 9 is in theprocess of being moved downward at a position which is apart from theelevating plate 10. Accordingly, only the pressing force by the outerslide 8 is applied to the blank W via the elevating plate 10 and theupper die 7, and the outer slide 8 is at the substantial bottom deadcenter by the drive portion 14 at this time so as to await the downwardmovement of the inner slide 9.

Further, when the first hydraulic cylinder 11 is contracted by thepressing force caused by the downward movement of the inner slide 9 asshown in FIG. 7(C), the second hydraulic cylinder 12 is expanded by theeffect of the pressure fluid pushed out from the first hydrauliccylinder 11, in specific, the cylinder barrel 12A (refer to FIG. 5) ofthe second hydraulic cylinder 12 is moved downward while pressing theouter slide 8 to the lower side, at the same time when the pressingforce of the inner slide 9 is applied to the elevating plate 10 via thefirst hydraulic cylinder 11. Accordingly, the elevating plate 10 ispressed in the respective portions of the upper surface by the outerslide 8 and the inner slide 9 so as to be moved downward. As a result,it is possible to well press mold the blank W between the upper die 7mounted to the lower surface of the elevating plate 10 and the lower die3 on the bolster under a high pressure, while preventing the strain ofthe elevating plate 10.

When the press molding of the blank W is finished as mentioned above,the outer slide 8 and the inner slide 9 are returned to the initialposition (the top dead center) as shown in FIG. 7(D), however, thesecond hydraulic cylinder 12 is returned to the contracted state by thepressurized fluid flowing out from the secondary port at this time, andthe first hydraulic cylinder 11 is returned to the expanded state by thepressurized fluid discharged from the primary port.

In this case, FIG. 8 is a cycle curve of the outer slide 8 and the innerslide, in which a single-dot chain line shows a stroke of the outerslide 8 with respect to an angle of rotation (deg) of the crank shaft19, and a solid line shows a stroke of the inner slide 9 in the samemanner. As is apparent from the drawing, the outer slide 8 is moveddownward prior to the inner slide 9, and is moved upward later than theinner slide 9. In particular, the outer slide 8 is temporarily stoppedat the substantial bottom dead center while leaving an expansion strokeS of the second hydraulic cylinder 12, and is moved downward at thestroke S by being pressed by the second hydraulic cylinder 12 expandedas mentioned above, at a time when the inner slide 9 reaches the bottomdead center.

As mentioned above, in accordance with the mechanical press apparatus onthe basis of the present invention, it is possible to apply the greatpressing force by the outer slide 8 and the inner slide 9 to therespective portions on the upper surface of the elevating plate 10 fixedto the lower end surface of the outer slide 8, while being of the doubleaction type in which the outer slide 8 and the inner slide 9 areindependently driven, and it is possible to well press mold the blank Wby the upper die 7 mounted to the lower surface of the elevating plate10 while preventing the strain of the elevating plate 10.

The descriptions are in detail given above of the embodiments of themechanical press apparatus in accordance with the present invention,however, the present invention is not limited to the embodiments, forexample, the mechanical press apparatus mentioned above can be appliedto a knuckle press, a link press, a friction press or the like withoutbeing limited to the crank press that the transmission mechanism of thedrive portion 14 is the crank mechanism.

1. A mechanical press apparatus provided with a drive portion whichmoves upward and downward an outer slide and an inner slide arranged inan inner side of the outer slide at a predetermined timing,characterized in that the mechanical press apparatus comprises: anelevating plate fixed to a lower end surface of said outer slide so asto oppose to a lower surface of said inner slide; an upper die (an uppermold) fixed to a lower surface of said elevating plate; a lower die (alower mold) positioned at a lower surface of an upward and downwardmovement of said upper die so as to press; a first hydraulic cylinderprovided in an upper surface portion of said elevating plate andcontracted by a pressing force at a time when said inner slide movesdownward; and a second hydraulic cylinder interposed between said outerslide and said drive portion and expanded working with a pressure of apressurized fluid supplied from said first hydraulic cylinder at a timewhen said first hydraulic cylinder is contracted by the pressing forceof said inner slide, thereby pressing said outer slide to a lower side.2. A mechanical press apparatus as claimed in claim 1, characterized inthat each of said first hydraulic cylinder and said second hydrauliccylinder is of a single rod type having an expansion rod integrallyprovided with a piston portion which is reciprocated in a longitudinaldirection in an inner portion of a hollow and sealed cylinder barrel soas to expand and compress a fluid in an inner portion, and a rod portionwhich is extended from the piston portion to an outer portion of saidcylinder barrel, and of a double action type having a primary portsupplying and discharging the expanded and compressed fluid to a side ofthe piston portion of said expansion rod and a secondary port supplyingand discharging the fluid in a side of the rod portion of said expansionrod in said cylinder barrel, and the cylinder barrels of the firsthydraulic cylinder and the second hydraulic cylinder are connected insaid primary ports to each other via a consecutive passage, and workwith each other such that the pressurized fluid flows into said secondhydraulic cylinder via said consecutive passage at a time when saidfirst hydraulic cylinder is contracted, thereby expanding said expansionrod.
 3. A mechanical press apparatus as claimed in claim 1 or 2,characterized in that a rate A1/A2 between a pressure receiving area A1of said first hydraulic cylinder (the piston portion) and a pressurereceiving area A2 of said second hydraulic cylinder (the piston portion)is set to be equal to a rate P1/P2 between a pressing capacity P1 ofsaid inner slide and a pressing capacity P2 of said outer slide.
 4. Amechanical press apparatus as claimed in claim 2, characterized in thata first pipe line for supplying the pressurized fluid having apredetermined pressure from a pressure source is connected to an area ofsaid consecutive passage connecting the primary ports of said firsthydraulic cylinder and said second hydraulic cylinder to each other, asecond pipe line for supplying the pressurized fluid having a higherpressure than that of the pressurized fluid supplied to said first pipeline from said pressure source so as to return to said state beforebeing communicated is connected to the secondary port of said secondhydraulic cylinder, and the secondary port of said first hydrauliccylinder is provided so as to supply and discharge an air serving as thefluid in correspondence to said motion thereof.
 5. A mechanical pressapparatus as claimed in claim 2, characterized in that said firsthydraulic cylinder is provided so as to be actuated only by said primaryport with canceling said secondary port.
 6. A mechanical press apparatusas claimed in claim 2, characterized in that an accumulator (a pressureaccumulator) is provided in the secondary port of said second hydrauliccylinder.
 7. A mechanical press apparatus as claimed in claim 1,characterized in that a die set portion for coupling said upper die isprovided in the lower surface of said elevating plate.
 8. A mechanicalpress apparatus as claimed in claim 4, characterized in that a checkvalve for preventing the pressurized fluid from flowing backward withrespect to said pressure source, and a pressure control valve arrangedin a downward side of said check valve are respectively interposed insaid first pipe line and the second pipe line, and a working pressure ofthe pressure control valve in said first pipe line is set higher thanthat of the pressure control valve in said second pipe line.